It is known that organic polymers having at least one reactive silyl group in the molecule, by nature, are crosslinked by siloxane bond formation, which involves the hydrolysis and other reactions of the silyl group due to factors such as moisture even at room temperature, thereby forming rubbery cured products. Such reactive silyl group-containing organic polymers whose backbone is a polyoxyalkylene polymer or a polyisobutylene polymer have been produced on an industrial scale and widely used in applications such as sealants, adhesives, and paints (Patent Literatures 1 and 2). When reactive silyl group-containing organic polymers are used in curable compositions for sealants, adhesives, paints, or other similar applications, they are required to have various properties such as curability and adhesion as well as mechanical properties of the cured products.
Curable compositions containing reactive silyl group-containing organic polymers are usually used in combination with condensation catalysts such as organotin compounds having a carbon-tin bond, typically, dibutyltin bis(acetylacetonate) or dibutyltin dilaurate. Recently, however, the toxicity of organotin compounds has been pointed out, and thus suggestions have been made for using as condensation catalysts other than organotin compounds catalyst systems such as carboxylic acid tin salts or other carboxylic acid metal salts, combinations of carboxylic acids and amine compounds, or amine compounds. However, the use of even metals other than tin can be undesirable depending on the application, and the combined use of carboxylic acids and amine compounds has a problem in that it is less likely to result in high cure rate. Among the above catalyst systems, highly basic amine compounds have been found to be excellent in the balance of physical properties such as curability and adhesion (Patent Literatures 3 and 4).
Meanwhile, it has been found that when an amine compound is used as a curing catalyst, a polymer having a specific chain end structure can be used to prepare a curable composition that exhibits a high cure rate (Patent Literatures 5 and 6). However, cured products of curable compositions containing polymers as disclosed in Patent Literatures 5 and 6 tend to show low elastic recovery and thus require some improvement when they are used as construction sealants where significant movement of the joints occurs.